1. Technical Field
The present invention relates generally to devices for laying pipe and, more specifically, to a device that advances along the course of pipeline construction, lays and joins pipe.
2. Background of the Invention
The process of laying sections of pipe along the course of pipeline construction when a bell and spigot pipe is being installed, involves laying sequential pipe lengths and the joining the sequential pipe lengths by applying a mechanical pressure to a most recently laid section of pipe in order to engage the spigot end of that length with the bell end of a previously laid length. When the course of pipeline construction lies underground, construction involves the excavation of a trench to a desired depth followed by placement and positioning of pipe in the trench. This method involves placing one or more workers in the trench to guide a lowered section of pipe into contact with a previously installed section. The workers must also disengage rigging from the pipe that was used in lowering the length into the trench. Once a pipe length is positioned in the trench, it is manually joined to a preceding pipe length. In deep trenches, a work crew commonly works within the confines of a trench shoring box that provides increased safety in the trench working condition.
Excavation and placement functions are typically performed by a single piece of equipment, an excavator. The excavator is a relatively costly piece of equipment, often track mounted, that performs primarily an excavation function. One disadvantage of the current popular method is the fact that a costly piece of equipment is oftentimes moved between tasks, excavation and pipe installation, that may otherwise proceed at different rates. Additionally, where shoring is required it is often moved along the length of the trench by the excavator as the pipeline advances requiring yet a third function or task of the excavator.
Devices, including excavators that position or otherwise place pipe at the bottom of a trench, pose a number of disadvantages. These devices are positioned outside the trench and typically place pipe by maneuvering along a top edge of the trench over tailings that have been placed alongside the trench during excavation. These surfaces are rarely, if ever, flat and therefore make the task of placement more difficult. Additionally, activity at grade level, depending on soil conditions, may increase a probability of trench collapse. Additional problems are seen when laying bell and spigot pipe. For instance, manufacturer's and job specifications typically require that the spigot end of a first pipe length be inserted into a bell end of a sequential pipe length a specified distance and that the spigot end not be “bottomed” out in the bell end when inserted. Additionally, manufacturer's and job specifications typically require that when the pipe is laid on a substrate that a “divot” be provided for the bell end to lay in so that undue stress is not created in the pipe at the transition of the bell to the barrel of the pipe due to the differing diameters of the bell and the barrel portions of the pipe.
Advantage may therefore be found in providing a device that is capable of laying and joining pipe in a trench. Additional advantage may be found in providing an apparatus that advances along the course of pipeline construction, for instance a pre-excavated trench, laying and joining pipe in the trench. Advantage may also be found in providing a device that aligns sequential lengths of bell and spigot pipe and seats a spigot end of a first pipe length into the bell end of a sequential pipe length. Additional advantage may be found in providing an apparatus that provides a divot for the bell to lie in as the device proceeds along the course of pipeline construction.